Add article for Qt Creator setup

Add article for how to setup Qt Creator for the toolchain.

---

Build environment example
```
SDKTARGETSYSROOT=/opt/codex/rm10x/3.1.15/sysroots/cortexa9hf-neon-remarkable-linux-gnueabi
PKG_CONFIG_SYSROOT_DIR=${SDKTARGETSYSROOT}
PKG_CONFIG_PATH=${SDKTARGETSYSROOT}/usr/lib/pkgconfig:${SDKTARGETSYSROOT}/usr/share/pkgconfig
CONFIG_SITE=/opt/codex/rm10x/3.1.15/site-config-cortexa9hf-neon-remarkable-linux-gnueabi
OECORE_NATIVE_SYSROOT=/opt/codex/rm10x/3.1.15/sysroots/x86_64-codexsdk-linux
OECORE_TARGET_SYSROOT=${SDKTARGETSYSROOT}
OECORE_ACLOCAL_OPTS=-I ${OECORE_NATIVE_SYSROOT}/usr/share/aclocal
OECORE_BASELIB=lib
OECORE_TARGET_ARCH=arm
OECORE_TARGET_OS=linux-gnueabi
CC=arm-remarkable-linux-gnueabi-gcc -mfpu=neon -mfloat-abi=hard -mcpu=cortex-a9 --sysroot=${SDKTARGETSYSROOT}
CXX=arm-remarkable-linux-gnueabi-g++ -mfpu=neon -mfloat-abi=hard -mcpu=cortex-a9 --sysroot=${SDKTARGETSYSROOT}
CPP=arm-remarkable-linux-gnueabi-gcc -E -mfpu=neon -mfloat-abi=hard -mcpu=cortex-a9 --sysroot=${SDKTARGETSYSROOT}
AS=arm-remarkable-linux-gnueabi-as
LD=arm-remarkable-linux-gnueabi-ld --sysroot=${SDKTARGETSYSROOT}
GDB=arm-remarkable-linux-gnueabi-gdb
STRIP=arm-remarkable-linux-gnueabi-strip
RANLIB=arm-remarkable-linux-gnueabi-ranlib
OBJCOPY=arm-remarkable-linux-gnueabi-objcopy
OBJDUMP=arm-remarkable-linux-gnueabi-objdump
READELF=arm-remarkable-linux-gnueabi-readelf
AR=arm-remarkable-linux-gnueabi-ar
NM=arm-remarkable-linux-gnueabi-nm
M4=m4
TARGET_PREFIX=arm-remarkable-linux-gnueabi-
CONFIGURE_FLAGS=--target=arm-remarkable-linux-gnueabi --host=arm-remarkable-linux-gnueabi --build=x86_64-linux --with-libtool-sysroot=${SDKTARGETSYSROOT}
CFLAGS= -O2 -pipe -g -feliminate-unused-debug-types
CXXFLAGS= -O2 -pipe -g -feliminate-unused-debug-types
LDFLAGS=-Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed
CPPFLAGS=
KCFLAGS=--sysroot=${SDKTARGETSYSROOT}
OECORE_DISTRO_VERSION=3.1.15
OECORE_SDK_VERSION=3.1.15
ARCH=arm
CROSS_COMPILE=arm-remarkable-linux-gnueabi-
OPENSSL_CONF=${OECORE_NATIVE_SYSROOT}/usr/lib/ssl-1.1/openssl.cnf
OE_QMAKE_CFLAGS=$CFLAGS
OE_QMAKE_CXXFLAGS=$CXXFLAGS
OE_QMAKE_LDFLAGS=$LDFLAGS
OE_QMAKE_CC=$CC
OE_QMAKE_CXX=$CXX
OE_QMAKE_LINK=$CXX
OE_QMAKE_AR=$AR
OE_QMAKE_STRIP=$STRIP
QT_CONF_PATH=${OECORE_NATIVE_SYSROOT}/usr/bin/qt.conf
OE_QMAKE_LIBDIR_QT=/opt/codex/rm10x/3.1.15/sysroots/cortexa9hf-neon-remarkable-linux-gnueabi/usr/lib
OE_QMAKE_INCDIR_QT=/opt/codex/rm10x/3.1.15/sysroots/cortexa9hf-neon-remarkable-linux-gnueabi/usr/include
OE_QMAKE_MOC=${OECORE_NATIVE_SYSROOT}/usr/bin/moc
OE_QMAKE_UIC=${OECORE_NATIVE_SYSROOT}/usr/bin/uic
OE_QMAKE_RCC=${OECORE_NATIVE_SYSROOT}/usr/bin/rcc
OE_QMAKE_QDBUSCPP2XML=${OECORE_NATIVE_SYSROOT}/usr/bin/qdbuscpp2xml
OE_QMAKE_QDBUSXML2CPP=${OECORE_NATIVE_SYSROOT}/usr/bin/qdbusxml2cpp
OE_QMAKE_QT_CONFIG=${OE_QMAKE_LIBDIR_QT}/mkspecs/qconfig.pri
OE_QMAKE_PATH_HOST_BINS=${OECORE_NATIVE_SYSROOT}/usr/bin
QMAKESPEC=${OE_QMAKE_LIBDIR_QT}/mkspecs/linux-oe-g++
PATH=${OECORE_NATIVE_SYSROOT}/usr/bin:${OECORE_NATIVE_SYSROOT}/usr/sbin:${OECORE_NATIVE_SYSROOT}/bin:${OECORE_NATIVE_SYSROOT}/sbin:${OECORE_NATIVE_SYSROOT}/usr/bin/../x86_64-codexsdk-linux/bin:${OECORE_NATIVE_SYSROOT}/usr/bin/arm-remarkable-linux-gnueabi:${OECORE_NATIVE_SYSROOT}/usr/bin/arm-remarkable-linux-musl:${PATH}
```